Die for swaging screws



' (No Model.)

B. A. KENNEDY.

DIE FOR SWAGING SCREWS.

Patented Mar. 23, 1886 UNITE STATES arena? UFFICE.

BURR A. KENN DY, OF LAKE view, ILLINOIS.

DIE FDR SVVAGENG SCREWS.

SPECIFICATION forming part of Letters Patent No. 338,276, dated March23, 1886.

Application filed January 5, 1885.

T0 aZZ whom it may concern:

Be it known that I, BURR A. KENNEDY, of the town of Lake View, in thecounty of Cook and State of Illinois, have invented certain new anduseful Improvements in Dies for Forging Screws, of which the followingis a full description, reference being had to the accompanying drawings.

The object of this invention is to make the forging of screw-threadspractical as distinguished from those made by cutting out the grooves,as with dies.

As shown, my method of forging is better adapted to the making of whatis known as the half-V thread, but any other can be formed by properadaptation of the dies.

In the drawings, Figurel shows the blank from which the form of screwshown in Fig. 2 is forged. Fig. 3 is aperspective view of the operatingparts of an ordinary trip-hammer to which my dies are attached. Fig. 4is a face View of the upper die, and Fig. 5 is aface View of the lowerdie. Fig. 6 is an end view of the lower die. Fig. 7 showsa simple formof screw used for piano-stools, for the production of which the methodand dies here shown are well adapted.

A is the helve of the trip-hammer.

A is the upper die-block.

A is the upper die.

B is the anvil-block.

B is the lower die-block, and B the lower die. Each die is provided witha form or recess for roughly shaping the thread, and another form orrecess for finishing the thread.

0 and G are the two shaping-forms, which are of corresponding orcomplementary shape, and D D the finishingforms, which are alsocomplementary. The shaping-forms O G are of semicircular form incross'section, so that a circular opening is presented between them whenthey are closed together. Each of these forms is of diminishing sizefrom the end at which the blank is received to the opposite end at whichthe blank is delivered. The walls of these shaping-forms G O areprovided with screw-threads approximating in form and size, the threadsbeing of the required scope, and their diameter at the smaller end beingvery slightly greater than required on the finished screw. The heatedbar or blank is Serial No. 152,094. (No model.)

passed endwise between the dies while the hammer is in motion, beingentered between the larger ends of the forms 6 G and turned graduallyforward. In this manner a screwthread is gradually beaten into theblank, the form and depth of the thread being gradually developed as theblank proceeds through the forms from the larger toward the smaller end.On emerging from the dies the screw presents the appearance presented inFig. 2, with a well formed but as yet unfinished thread thereon.

D D are the finishingforms, having internal threads of the size anddepth corresponding precisely with those of the screw to be produced.These finishing -forms are commonly ofuniform diameter from end to end,with several threads or convolutions of a thread therein, as shown inthe drawings, so that the screw may be kept straight while beingfinished thereby. The rough screw, on leaving the forms G G, issubjected to the action of the forms D D, which serve to reduce it tothe exact size and to give the threads that accuracy and smoothness offinish which is necessary to its proper action when in use. It ispreferred to have the roughened forms G O and the finishing forms D Ddistinct from each other, as shown in the drawings; but if preferred thefinishing forms may be arranged in line with and as coutinuations of theroughening-form, in which case thescrew will be finished in a singlepassage between the dies.

i D and Dare the finishing-dies,being matrices formed with threads ofsize and depth exactly equal to the finished screw to be. Thisfinishing-die is made of several threads in length, so that as the screwpasses through it is kept straight.

For the form of screw shown in Fig. 2 the blank shown in Fig. 1 isprepared. I prefer to make the stems e and c of this blank of a sizeslightlylless than the diameter of the screw at the bottom of thethreads. These stems may then be thrust between the dies, even while thehammer is in motion, and they form a guide to direct the thread, alreadyroughly made, into the finishing-dies as it is pressed forward andturned to screw it in. Were not some such provision made it would bevery difficult, if not impossible, to place the screw ceiving toward thedelivery side,wl1ereby the in the finishing-die without stopping theham- In order that a screw like that shown in Fig. 7 may be made toenter the die while the hammer is in operation, the dies have anunthreaded space, f and f, of diameter equal to that of the shank of thescrew. Into this the end of the screw is laid, and as it is pressedforward and. slowly rotated it is screwed into the die and smoothed. Itis preferable to make the screw a little larger than the finishing-dies,so that the latter will have stock to work on, as this produces smootherwork.

In coach-screws and other coarse screws the finishing-dies may not berequired, the forming-dies being sufficient.

It is not necessary to make the finishingdies (when they are used) inthe same block; but I consider it best to so have them, as the wholeoperation of forming and finishing may be performed at the sameoperation.

In order to avoid the throwing out'of fins on the work, I relieve theends of the threads, as shown in Fig. 6, at g and g and at h and h.

In order that the first effect of the formingdie mayact the more tothrow the threads upwardthat is, to make the metal fill the die ratherthan to draw the blank and thus lengthen it--I corner the threads 1, 2,and 3, so that they may have tendency but to crease the metal. This Ifind a necessity in some cases, and desirable in all.

What I claim is 1. The herein-described method of forming screw-threads,consisting in passing the blank slowly in an endwise direction between apair of converging dies, which are threaded internally and reduced indiameter from the rethreads are gradually developed on the blank.

2. A pair of screw converging dies with complementary forms or cavitiestherein,said cavities diminishing in size from the receiving toward thedelivery side of the dies, and provided with internal threads ofincreasing size from the receiving toward the delivery side, wherebyeach portion of the thread upon the blank may be gradually developed asit is presented to the developing portions of the die-thread.

3. As an improvement in the art of forging screw-threads, the methodconsistingin first passing the blank between tapering internallythreadedforming-surfaces, and subsequently between forming-surfaces of smallerinternal diameter having threads of constant form and size therein.

4. Complementary screw-forging dies provided with taperinginternally-threaded forms or cavities to produce the crude thread, andthe finishing-form of smaller internal diameter threaded in exactconformity to the re; quired screw.

5. lChe complementary dies for finishing screw-threads, having theinternal forms or unthreaded recesses, F F, of semicircular section anduniform diameter, and the internal threads of uniform size throughouttheir entire length, whereby said dies are adapted to finish the threadsfor use and at the same time to maintain the screw in a perfectlystraight condition.

BURR A. KENNEDY.

Witnesses:

ROBERT H. DIXON, JOHN B. KASPARI.

